James Lee DiMaggio used timer to set house fire that began hours after he fled with Hannah Anderson

SAN DIEGO -- A family friend who kidnapped a 16-year-old girl had a 20-hour jump on authorities, who discovered he used a timer to set fire to his rural home where the girl's mother and younger brother were found dead, a San Diego County Sheriff's Department spokeswoman said Tuesday.

James Lee DiMaggio was spotted on a Border Patrol surveillance camera at 12:10 a.m. Aug. 4, about 20 hours before his home caught fire, said the spokeswoman, Jan Caldwell. He is seen inside his 2013 blue Nissan Versa with 16-year-old Hannah Anderson at a westbound highway checkpoint.

Hannah's disappearance -- discovered after the fire -- triggered a massive search for DiMaggio, 40, that spanned much of the western United States and parts of Canada and Mexico. DiMaggio, who was like an uncle to the Anderson children and their father's best friend, died in a shootout with FBI agents in the Idaho wilderness six days after the fire. Hannah was rescued and returned to Southern California.

The discovery that the fire was set by a timer prompted investigators to warn the public during the manhunt that DiMaggio's car might be rigged with explosives, Caldwell said. As it turns out, the car wasn't rigged.

Investigators who searched DiMaggio's home found an incendiary device, handcuff boxes and "arson wire," according to a search warrant. It also says they discovered letters from Hannah and a handwritten note, without elaborating on the contents.

Search warrants unsealed last week said Hannah was picked up from a cheerleading practice at 4 p.m. on Aug. 4, but Caldwell said the practice was a day earlier.

Firefighters found the body of Christina Anderson, 44, when they extinguished flames at DiMaggio's home in Boulevard, a tiny town about 65 miles east of San Diego on the U.S.-Mexico border. A search warrant says she was found near a crowbar and what appeared to be blood next to her head.

The San Diego County Medical Examiner's Office said she died of a blunt head injury, without elaborating on the nature of the wound or the circumstances of her death in a posting to its website. The manner of death is listed as homicide.

Investigators found 8-year-old Ethan Anderson's body as they sifted through rubble. Authorities identified his remains several days later by extracting DNA from his bone marrow.

The medical examiner's office said Tuesday that the cause and manner of the boy's death remained under investigation.